This invention relates to a resist material usable in the production of semiconductor elements. More particularly the present invention relates to a resist material used in the formation of a positive tone pattern using deep ultraviolet (UV) light of 300 nm or less such as KrF excimer laser light, etc.
With recent higher density and larger scale integration of semiconductor devices, wavelengths used in exposing devices for minute processing, particularly for lithography become shorter and shorter. Now, KrF excimer laser light (248.4 nm) is studied. But, there have been no photosensitive materials suitable for use as such a wavelength.
For example, there are proposed dissolution inhibiting type resist materials comprising a resin having high transmittance for light of near 248.4 nm and a photosensitive compound having a group of the formula: ##STR1## as a resist material for a light source such as KrF excimer laser light and deep UV light (e.g. Japanese Patent Unexamined Publication Nos. 1-80944, 1-154048, 1-155338, 1-155339, and 1-18852; Y. Tani et al: SPIE's 1989 Sympo., 1086-03, etc.). But, these dissolution inhibiting type resist materials are low in sensitivity, and thus cannot be used for deep UV light and KrF excimer laser light which require highly sensitive resist materials.
On the other hand, in order to reduce the exposure energy amount (so as to increase the sensitivity), chemical amplified resist materials we recently have proposed wherein an acid generated by exposure to light is used as a catalyst [H. Ito et al: Poly. Eng. Sci. vol. 23, page 1012 (1983)]. Various chemical amplified resist materials are reported, for example, in U.S. Pat. Nos. 4,491,628 and 4,603,101, Japanese Patent Unexamined Publication No. 62-115440, W. R. Brunsvold et al: SPIE's 1989 Sympo., 1086-40, T. Neenan et al: SPIE's 1989 Sympo., 1086-01, etc. But these chemical amplified resist materials have the following disadvantages. When phenol ether type resins such as poly(4-tert-butoxycarbonyloxystyrene), poly(4-tert-butoxycarbonyloxy-.alpha.-methylstyrene), poly(4-tert-butoxystyrene), poly(4-tert-butoxy-.alpha.-methylstyrene) are used, heat resistance is poor, and resist films are easily peeled off at the time of development due to poor adhesion to substrates, resulting in a failure to obtain pattern shapes. Further, when carboxylic acid ester type resins such as poly(tert-butyl-4-vinylbenzoate), etc. are used, the transmittance for light of near 248.4 nm is poor due to the aromatic rings of the resin. When poly(tert-butylmethacryalte) and the like is used as the resin, heat resistance and resistance to dry etching are poor. As mentioned above, the chemical amplified resist materials have higher sensitivity than known resist materials, but are poor in heat resistance of resin, poor in adhesiveness to substrates, and insufficient in transmittance for light of near 248.4 nm, resulting in making practical use difficult. Thus, practically usable highly sensitive resist materials overcoming these problems mentioned above are desired.